Field of the Invention
The present invention relates to a sputtering device including a plurality of targets and a plurality of cathodes that forms a thin layer on a surface of a long film substrate and a maintenance method for such a sputtering device.
Description of the Related Art
A sputtering method is widely used as a method for forming a thin layer on a surface of a long film substrate. In a sputtering device having a long film substrate, a layer forming roll and a plurality of targets are placed oppositely at predetermined intervals. A layer forming roll wound around by a long film substrate in a sputtering gas such as a low-pressure argon gas is referred to as an anode potential and a target is referred to as a cathode potential. A voltage is applied between the layer forming roll and the target to create a plasma in the sputtering gas between the layer forming roll and the target. Sputtering gas ions in plasma collide with the target to knock out components of the target. The knocked out components of the target deposit on the long film substrate to form a thin layer.
In the case of a long film substrate, it is impossible to form a sputtered layer over the whole of the long film substrate at a time. Accordingly, the long film substrate delivered from a supply roll is wound around the layer forming roll (can roll) by less than one round, and the layer forming roll is rotated to cause the long film substrate to continuously run. A thin layer is deposited on a portion of the long film substrate facing to the target. The long film substrate after completion of thin layer deposition is wound to a storage roll.
In general, a target is supported on a cathode by screw clamp. The target and the cathode are in identical potential. Since a target and a cathode are a pair (set), it is referred to as “a target and a cathode”. Screws are removed to separate the cathode from the target when replacing the target. As the thin film formation is promoted, the target exhausts. When the target exhausts in a predetermined amount, a new target has to be replaced. Contaminants, such as components of the target adhere to a cathode. When the contamination of the cathode becomes worse, abnormal electrical discharge is generated and impurities are mixed in a thin layer. Accordingly, the cathode needs to be cleaned before the contamination becomes worse. It is also preferable to separate the target and the cathode when cleaning the cathode.
In the case of a small-size sputtering apparatus, targets are easily replaceable by human power. In addition, the cleaning of cathodes is easy. However, in the current long film substrate included in the sputtering apparatus, the long film substrate has a width of about 1.6 m, so that the weight of targets and cathodes is some hundred Kgs. Since it is possible to handle the targets and the cathodes by human power, it is needed to use a crane or a lift when replacing the targets.
A plurality of targets are opposed to the layer forming roll at small intervals. This makes it difficult to remove the screw and replace the targets at a position where the targets are placed opposite to the layer forming roll. In a conventional maintenance method, first, a plurality of targets and a plurality of cathodes are placed on a cart for maintenance to be removed from a vacuum chamber. Next, a locking screw of each of old targets is taken off on a cart for maintenance to remove the old targets. Contamination of the cathodes is cleaned. And then new targets are screwed. Subsequently, the targets and the cathodes return to the predetermined position in the vacuum chamber by use of the cart for maintenance to be fixed.
As well as the conventional maintenance method has poor work efficiency, it is dangerous to transfer the big and heavy targets and cathodes to the cart for maintenance. Specifically, in a sputtering device equipped with a large number of targets and cathodes so as to surround a layer forming roll, it takes an extremely long time to carry out maintenance, resulting in a significant decrease in operation rates of the sputtering apparatus when the large number of targets and cathodes are taken off, old targets are removed, the cathodes are cleaned to attach new targets and work to replace the targets and the cathodes one by one.
Various measures have been taken related to the above-mentioned problem. For instance, Japanese Unexamined Patent Application Publication No. JP 10-036967 A and Japanese Unexamined Patent Application Publication No. JP 2002-060936 A disclose that a part of a wall of a vacuum chamber is an openable wall which is openable/closable and a plurality of targets and a plurality of cathodes are fixed to the openable wall. When the openable wall is moved in parallel with a central axis of the layer forming roll, the targets and the cathodes are removed from the vacuum chamber while the targets and the cathodes are fixed to the openable wall. And the targets are replaced to clean contamination of the cathodes. Subsequently, the openable wall is caused to move to the original position and the targets and the cathodes are caused to return to a predetermined position respectively (a position where the layer forming roll is surrounded) in the vacuum chamber. According to this maintenance method, since there is no need to transfer the targets and the cathodes to the cart for maintenance, work efficiency to take off the targets and the cathodes and return to the original position is excellent. In addition, there is a slight danger of work.
Alternatively, Japanese Unexamined Patent Application Publication No. JP 2006-322055 A discloses that a part of a wall of a vacuum chamber is an openeable wall that is openeable/closable and a plurality of targets and a plurality of cathodes are fixed to the openable wall via a hinge. When the openeable wall is caused to move in parallel with a central axis of a layer forming roll, the targets and the cathodes are removed from the vacuum chamber, keeping being fixed to the openable wall. Next, when the targets and the cathodes are opened in a direction perpendicular to the openeable wall by use of the hinge, a work area is expanded. And the targets are replaced to clean contamination of the cathodes. Subsequently, the openable wall is caused to move to the original position to return each of the targets and the cathodes to a predetermined position (a position where the layer forming roll is surrounded) in the vacuum chamber after the targets and the cathodes are caused to return to original angles thereof. According to this maintenance method, since there is no need to transfer the targets and the cathodes to a cart for maintenance, the work area is expanded. This enables to simultaneously replace a plurality of targets and clean a plurality of cathodes by two persons or more.